A prior art search was performed and disclosed the following U.S. patent references:
U.S. Pat. No. 3,098,446 discloses a ring 27 which holds wings of a missile in place. Ring 27 is physically removed before the missile is launched, unlike in the present invention where constraint 35 is passively disintegrated subsequent to launch by the effects of aerodynamic heating.
U.S. Pat. No. 3,174,430 shows dished plate 18 for restraining rocket wings. The plate is blown off by pressure from the rocket blast, not by aerodynamic heating as in the present invention.
U.S. Pat. No. 3,756,602 discloses an arrow with vanes that are fixed with respect to the shaft of the arrow, not gimballed wings as in the present invention. The aerodynamic problems faced by archers are different than in the technical field addressed by the present invention, because in archery the velocity of the crossflow is not a linear function of the velocity of the relative wind.
U.S. Pat. No. 3,946,638 discloses sleeve 26 which holds rocket fins closed prior to launch. Sleeve 26 is left in the launch tube during launch and thus is not passively removed subsequent to launch by aerodynamic heating as is constraint 35 in the present invention.
U.S. Pat. No. 4,198,016 shows two pivotable canards 12 positioned on the outside of an underwater missile. The missile does not have a penetrator rod as in the present invention. The canards serve to create a counterforce on the nose of a missile by making an angle of attack with the relative "wind". The present invention optionally aligns wings to form an angle of attack with respect to the crossflow, but not with respect to the relative wind; and the wings are coupled to a penetrator rod.
Elongated penetrator rods such as rod 3 of the present invention have been used in the design of weapon systems for the perforation of armor plate. The parameters of primary importance in such a penetrator rod are: the specific energy placed upon the target surface and the degree of alignment of the rod's principal axis with the velocity vector of flight. The first of these parameters is optimized by designing the rod to have a high length-to-diameter ratio. The second parameter, alignment, becomes more critical as the length-to-diameter ratio increases. Tests have revealed that the alignment effects are severe: that is, a very small misalignment can result in a large reduction in target material penetration.
Long rod penetrator devices have been deployed on projectiles fired from a high velocity gun. In this non-guided application, the rod is structurally supported by a sabot while in the gun barrel, but flies free upon emergence. The rod is provided with some suitable aerodynamic surface, such as fins or a flared base, forming an aerodynamically stable airframe. The free unguided flight is accomplished, therefore, with near perfect alignment of the rod's principal axis and its velocity vector. Angular errors due to crossflow and/or target motion are intrinsically present, but are nominally very small due to the high projectile velocities typically involved (4000 to 5000 feet per second).
Beginning with the late 1970's, guided warheads (both missiles and projectiles) employing long rod penetrators as a lethal device have emerged. Typically, the penetrator is made integral with the structure of the warhead's airframe, and aligned with the longitudinal axis of the airframe. The airframe, in order to respond to guidance error commands, must develop a velocity vector component that is orthogonal to the uncorrected velocity vector of the warhead. This cross velocity may, but not necessarily, involve an attitude change as well; as a result, the airframe longitudinal axis may not be aligned with either the uncorrected velocity vector or the corrected velocity vector. As the penetrator principal axis and the airframe longitudinal axis are congruent, the penetrator may be misaligned with the corrected velocity vector. As a result, the performance of the warhead is sharply degraded.
Allowing an aerodynamically stable guided warhead to become unguided during the last period of flight can remove the guidance-error-induced misalignment of the rod, but at the expense of terminal accurancy and system complexity needed to determine the time of ballistic flight conversion.
The above problems are remedied by the present invention.